In the use of a welding torch, it is desirable to cool the torch as much as possible in order to substantially prevent damage to said torch from the elevated temperatures of the welding operation and from weld spatter.
For example, in arc welding operations involving the use of gas for shielding the arc area of the weld, a conventional welding torch typically has a nozzle and a contact tip. During welding, wire passes through and is supported by the contact tip which is positioned directly adjacent the weld area. The nozzle directs gas supplied to the torch, such as carbon dioxide gas, into the weld area for shielding purposes. The gas is generally supplied from a supply tank through hoses to the torch or, alternately, can also be supplied in liquid form to a location upstream of the torch where it is gasified before entering the torch.
In the torch, the nozzle is connected to a body of the torch and the contact tip is connected to a central guide housing. Both the contact tip and guide housing are positioned inside the torch body and are insulated from the nozzle and torch body. Electrical current is passed through the central guide housing and contact tip to the electrode wire to provide the electrical potential between the wire and work piece necessary in arc welding operations.
The contact tip and nozzle, positioned immediately adjacent the weld area, are directly exposed to the elevated temperatures of welding. During such operations, it is desirable to cool both the nozzle and the contact tip to prevent "burn through" owing to the high welding temperatures and to prevent build-up of weld spatter both of which can result in frequent replacement of the nozzle or contact tip and interference with gas flow to the arc area.
Heretofore, the contact tip has been cooled typically by liquid, generally water, circulated through the guide housing and adjacent the contact tip. The nozzle is air cooled except for indirect cooling effects from the guide body through the insulated area between the nozzle and guide body. Such welding torch construction is disclosed in U.S. Pat. Nos. 3,689,733 which issued to Matarovic on Sept. 5, 1972, and 3,529,126 which issued to Reeh on Sept. 15, 1970. Matarovic also uses the shielding gas supplied to the torch to cool the outer or handle portion of the torch by directing the flow of gas through a portion of the torch associated with the handle. U.S. Pat. No. 3,253,116 which issued to Kensrue on May 24, 1966, alternately discloses the use of air for cooling a welding torch.
Another type of welding involving problems of elevated temperature is that which does not require gas for shielding purposes, such as in electro-slag welding. The typical welding torch does not, therefore, generally make use of a nozzle. The contact tip is connected directly to the body through a mounting assembly and the electrical current passes through the body and contact tip to the wire. Cooling of the contact tip and the mounting assembly is also important to prevent damage to the welding torch owing to problems similar to those discussed above which are associated with the high temperatures created in the welding process.
The cooling of the above described welding torches, particularly in a heavy duty cycle of automated or robot welding, is sometimes not adequate. It is therefore desirable to provide apparatus to more directly cool the contact tip and the associated mounting element or nozzle, where present.
It will be appreciated that the use of liquids, which absorb heat during gasification, in direct association with the nozzle or contact tip can provide cooling of said elements during the gasification process.
U.S. Pat. No. 2,870,320 which issued to Matthews on Jan. 20, 1959, discloses the principle of gasifying liquid to cool a welding torch. Also, liquid used to create the plasma for a plasma torch is shown being utilized to provide some cooling to the plasma torch in U.S. Pat. No. 3,217,133 which issued on Nov. 9, 1965, to Matmuller.
Such use of liquids is particularly true with such liquids as carbon dioxide which absorb a relatively high amount of heat energy during gasification. Thus, preferably, liquid can be supplied into the welding torch and directly onto the nozzle, contact tip or elements closely associated thereto for gasification owing to the elevated temperatures of welding at said components of the torch. Use of liquids, however, is not without problems. For example, the use of carbon dioxide, or similarly acting coolants which exhibit instability in their liquid phase, can result in some solid material or "snow" being created which can block the torch and prevent continuous operation.
The present invention is directed to overcoming one or more of the above-described problems.